Preparation of high molecular weight dialkyl aromatic compounds



3,538,l77 Patented Nov. 3, 1970 3,538,177 PREPARATION OF HIGH MOLECULAR WEIGHT DIALKYL AROMATIC COMPOUNDS Gene E. Nicks, Ponca City, Okla, assignor to Continental Oil Company, Ponca City, Okla, a corporation of Delaware No Drawing. Filed Sept. 25, 1968, Ser. No. 762,639 Int. Cl. C07c 3/00, 3/50; ClOm 3/10 US. Cl. 260--672 14 Claims ABSTRACT OF THE DISCLOSURE This disclosure concerns the disproportionation of mono-C -C -alkyl aromatic compounds to di-C C alkyl aromatic compounds using HF-BF as the catalyst. The aromatic moiety is phenyl, tolyl, xylyl, or naphthyl In a preferred aspect the disclosure concerns the disproportionation of monoalkylbenzenes to dialkylbenzenes, using HF-BF as the catalyst. The alkyl group of the monoalkylbenzenes and each of the alkyl groups of the dialkylbenzenes contains at least 8 carbon atoms. Preferably, the monoalkylbenzenes subjected to disproportionation are present in a composition which contains tetrahydronaphthalenes. Use of the Hi -BF, catalyst produces dialkylbenzenes with no significant increase in tetrahydronaphthalenes.

DISCLOSURE Related application The following application has the same assignee as the present application.

Ser. No. 529,284, filed Feb. 23, 1966, concerns the disproportionation of mono-n-alkyl (cg-C13) benzenes to di-n-alkyl (C C benzenes. It teaches that Friedel- Crafts catalysts can be used, with aluminum chloride being the preferred catalyst.

Background The present invention relates to a process of preparing synthetic hydrocarbon compositions having properties which render them particularly useful as lubricants in extremely low temperature operations.

Various petroleum fractions have been used as lubricants for many years. While the petroleum-derived lubricants have been satisfactory for most uses, there are fields of use, as for example, jet engine lubricants and arctic oils, wherein the requirements render the conventional petroleum-derived lubricants either unsatisfactory or of marginal utility. In an attempt to solve this problem synthetic lubricants (for example, diesters) have been developed having improved properties, particularly im proved viscosity and pour point properties. Unfortunately, the synthetic lubricants of the prior art have been relatively expensive. Because of this, recently there has been interest in developing synthetic hydrocarbon lubricants. The objective has been to develop lubricants having properties equal to or better than the diester-type lubricants yet which are less expensive.

US. Pat. 3,288,716 describes a synthetic hydrocarbon composition having properties which render it particularly satisfactory as a lubricant. The composition of this patent benzenes and 5 to 50 parts by volume diphenylalkanes.

In addition, other materials (e.g. tetrahydronaphthalenes) can be present.

One method of preparing a hydrocarbon composition, containing substantial amounts (e.g. above percent) of high molecular weight dialkylbenzenes is by disproportionation of monoalkylbenzenes. Unfortunately, commercially available monoalkylbenzenes, having the desired alkyl groups, are usually available in complex compositions containing other materials such as tetrahydronaphthalenes. Since an increase in the amount of tetrahydronaphthalenes increases the low temperature viscosity of compositions containing dialkylbenzenes and tetrahydronaphthalenes, it is desirable to have available means for minimizing the amount of tetrahydronaphthalenes produced in a disproportionation process.

The present invention provides a process which produces dialkylbenzenes from monoalkylbenzenes with no significant increase in tetrahydronaphthalene content.

Prior art US. Pat. 2,753,384, to Arthur P. Lien and David A. McCauley, teaches the disproportionation of monoalkylbenzenes to dialkylbenzenes using HF-BF as the catalyst. The alkyl groups are restricted to propyl and butyl. The patent teaches that n-butylbenzenes undergo cracking and other side reactions more readily than the n-propylben zenes. In view of this it would be expected that very little, if any, disproportionation of C monoalkylbenzenes would occur.

As stated in the foregoing I have discovered that use of HF-BF as the catalyst results in disproportionation of monoalkylbenzenes to dialkylbenzenes, in the presence of tetrahydronaphthalenes, Without an increase in the amount of these latter materials. This is not the case when the catalyst is aluminum chloride.

Moreover, I have discovered that not all Friedel-Crafts catalysts, particularly the weaker catalysts such as ferric chloride, BF alone, and aluminum chloride-nitrobenzene, produce a disproportionation of monoalkyl (Cg-C18) benzenes to the corresponding dialkylbenzenes.

BRIEF SUMMARY OF THE INVENTION Broadly stated, the present invention concerns a process for preparing di-C C alkyl aromatic compounds by contacting mono-C -C alkyl aromatic compounds with HF-BF catalyst and recovering the desired product from the reaction product.

In a preferred aspect, the present invention concerns a process for preparing dialkylbenzenes, having at least 8 carbon atoms in each of the alkyl groups, by contacting with HF-BF catalyst a hydrocarbon composition containing monoalkylbenzenes, having alkyl groups with the same number of carbon atoms: as said dialkylbenzenes, and tetrahydronaphthalenes, and recovering the dialkylbenzenes from the reaction product.

A salient feature of the process is the use of the HF-BF which results in disproportionation of monoalkylbenzenes to dialkylbenzenes in the presence of tetrahydronaphthalenes without an accompanying significant increase in the amount of the tetrahydronaphthalenes.

DETAILED DESCRIPTION Suitable materials for use as a starting material in my process are mono-C C -alkyl aromatic compounds, wherein the aromatic moiety is phenyl, tolyl, xylyl, or

naphthyl, but preferably is phenyl. Preferably the mono C C -alkyl aromatic compounds are mono-C C alkyl aromatic compounds.

A particularly suitable material is a composition containing a substantial amount of mono-n-alkylbenzenes produced in accordance with the process of U.S. Pat. No. 3,316,294. These mono-n-alkylbenzenes are characterized in that the alkyl substituents contain from 8 to 18 carbon atoms and at least 95 percent of the alkyl substituents are bonded to the benzene nucleaus through a secondary carbon atom of the respective alkyl group.

Briefly, US. 3,316,294 relates to a process of preparing a detergent alkylate, wherein the process comprises the following steps, broadly stated: (a) separating a fraction of substantially straight-chain C -C hydrocarbons from a petroleum distillate substantially free of olefins and containing said straight-chain hydrocarbons together with non-straight chain hydrocarbons, (b) chlorinating said fraction to the extent whereby between about 10 and about 35 mole percent of the straight-chain hydrog carbons present are substantially only mono-chlorinated, and (c) alkylating an aromatic compound, e.g. benzene, with the chlorination product of step (b) in the presence of an alkylation catalyst.

In order to make my disclosure even more complete US. Pat. No. 3,316,294 is made a part of this disclosure.

The monoalkylbenzene-containing composition can contain a minor amount (less than 25 percent, preferably less than 11 percent) of tetrahydronaphthalenes.

The term tetrahydronaphthalenes as used herein includes tetrahydronaphthalenes having alkyl substituents containing up to 8 carbon atoms.

The process of my invention uses a mixture of anhydrous liquid hydrogen fluoride and boron trifluoride. It is of interest that I have found that BF alone does not result in a product at all. Moreover, use of HF alone produces a product having properties which make it unsuitable for use as a jet engine or arctic lubricant.

The HF-BF catalyst should contain at least 2 parts by weight HF per part of BF Preferably the catalyst contains about 10 parts by weight HF per part of BF Larger amounts of HF can be used but no apparent benefit results and, of course, the cost is increased.

The amount of HF-BF used in my process should be from about weight percent to about 80 weight percent based on the monoalkylaromatic-containing charge material. Preferably, on the same basis, the amount of HF-BF should be from about 40 weight percent to about 60 weight percent.

Suitable reaction conditions for my proces are a temperature in the range of from about 0 C. to about 70 C., with a reaction time of from about 0.5 to about 6 hours. More suitable reaction conditions are a temperature in the range of from about 15 C. to about 35 C. with a reaction time of from about 1 to about 2.5 hours. With regard to the foregoing temperatures and times the longer time corresponds to the lower temperature. The preferred reaction conditions for my process are C. and 1.5 hours.

The recovery of the dialkylbenzene fraction from the reaction mixture can use conventional means. I have usually done this by first allowing the reaction mixture to settle and withdrawing the catalyst. The reaction mixture is then washed with a basic solution. Following the wash the reaction mixture is distilled to remove un unreacted monoalkylate and lighter materials. The cut point is dependent on the molecular weight of the monoalkylate charge material. When the monoalkylate is predominantly C monoalkylbenzene a cut point of 145 C. at 10 mm. Hg pressure is suitable. When the monoalkylate is predominantly C monoalkylbenzene a cut point of 197 C. at 10 mm. Hg pressure is suitable.

When the charge material is the monoalkylate fraction produced in accordance with US. 3,316,294, the product contains at least 80 percent (by weight) dialkylbenzenes and not more than 20 percent tetrahydronaphthalenes. Preferably, the product contains at least 85 percent dialkylbenzenes and not more than 15 percent tetrahydronaphthalenes.

The process of my invention produces at least a 20 percent (by weight) conversion of monoalkyl aromatic compounds to dialkyl aromatic compounds. More usually, the process produces at least a 30 percent conversion and usually at least a 40 percent conversion.

To those skilled in the art to which this invention relates the conversion of monoalkylbenzenes to dialkylbenzenes is referred to as a disproportionation reaction.

I have used the term no significant increase herein with regard to the amount of tetrahydronaphthalenes produced in the reaction. The term no significant increase, as used herein, is defined as being no more than about 30 percent, preferably about 15 percent, based on the tetrahydronaphthalenes originally present in the charge mixture.

As indicated previously, the product of my invention is particularly suitable for use as a lubricant having utility as jet engine lubricants and arctic oils. Usually, the product is used as a base stock which is blended with conventional additives such as oxidation-corrosion inhibitors and the like. If desirable the product can be blended with other base stocks to prepare a lubricant composition having specifically desired properties.

The product of my invention is also suitable as a sulfonation feedstock to prepare high quality oil-soluble sulfonates.

In order to disclose the nature of the present invention still more clearly, the following illustrative examples will be given. It is to be understood that the invention is not to be limited to the specific conditions or details set forth in these examples except insofar as such limitations are specified in the appended claims.

EXAMPLE 1 This example illustrates the preferred conditions of by process. The monoalkylate composition was produced by the process of US. 3,316,294 and had the following analysis:

Percent Monoalkylbenzene 89.5 Tetrahydronaphthalenes 10.5

ell-C34 alkyl groups, with a predominance of C13.

An amount of 900 grams of the monoalkylate composition was charged to an autoclave. The BP grams) and HP (500 grams) were then added to the autoclave. This reaction mixture was stirred for 1 hour with the temperature at 25 C. The reaction mixture was then settled and the catalyst withdrawn. The reaction product was washed with an aqueous base. Following this the reaction product was fractionally distilled using a cutpoint of 197 C. at 10 mm. Hg. The desired product (bottoms fraction) was water-white. It contained 87.7% dialkylbenzenes and 12.1% tetrahydronaphthalenes. it had the following physical properties:

Pour point, "P Viscosity at 40 F., cs. 6795 Viscosity at P., cs. 27.05 Viscosity at 210 F., cs. 4.93 Viscosity index 119 EXAMPLE 2 This is a comparative example which shows the elfect of using AlCl as the catalyst. The monoalkylate composition used as charge stock was the same as in Example 1.

An amount of 1500 grams of the monoalkylate composition was charged to an autoclave. To this were added 20 grams AlCl (1.3% by weight based on monoalkylate) and 0.3 gram water. The contents of the autoclave were stirred for 2 hours while maintaining the temperature at Tlle percent conversion of monoalkylbenzenes to dialkylbenzenes was 56%.

110 C. The reaction mixture was then settled and the catalyst withdrawn. The reaction product was washed with an aqueous base. Following this the reaction product was fractionally distilled using a cut-point of 197 C. at mm. Hg. The product (bottoms fraction) had a yellow to brown color. It contained 67.1% dialkylbenzenes 2 and 24.4% tetrahydronaphthalenes, with the remaining 8.5% being a mixture of naphthalenes, dihydronaphthalenes, and diphenylalkanes. The product had the following physical properties:

Pour point, F. M 65 Viscosity at F. 12,066

Viscosity at 100 F. 32.84 Viscosity at 210 F. 5.41 Viscosity index 110 EXAMPLE 3 This example is comparative and shows the eflect of using catalysts other than the HFBF complex. In all runs the monoalkylate composition was the same as in Example 1. The various catalysts tested and the results obtained are shown below.

Catalyst: Result Ferric chloride No disproportionation.

BF (alone) No disproportionation. AlCl -nitrobenzene No disproportionation.

HF (alone) Product had very high viscosity at 40 F.

BF -i-water No disproportionation. AlCl nitromethane No disproportionation.

While particular embodiments of the invention have been described, it will be understood, of course, that the invention is not limited thereto, since many modifications may be made; and it is, therefore, contemplated to cover by the appended claims any such modifications as fall within the true spirit and scope of the invention.

The percent conversion of monoalkylbenzenes to dialkylbenzenes was The invention having been described, what is claimed and desired to be secured by Letters Patent is:

1. A process for preparing di-C -C -alkyl aromatic compounds, the aromatic moiety of said compounds being phenyl, tolyl, xylyl or naphthyl, said process consisting essentially of:

(a) contacting mono C -C alkyl aromatic compounds, wherein the aromatic moiety is the same as that in the di-C -C alkyl aromatic compounds, with HF-BFg catalyst for from about 0.5 to about 6 hours at a temperature in the range of from about 0 to about 70 C.,

(b) recovering from the reaction product of step (a) said di-C C alkyl aromatic compounds.

2. The process of claim 1 wherein said C C alkyl groups are linear.

3. The process of claim 2 wherein the conversion of said mono-C C -alkyl aromatic to said di-C C -alkyl aromatic compounds is at least 20 Weight percent.

4. The process of claim 3 wherein the amount of HF- BF catalyst is from about 20 to about 80 Weight percent, based on said monoalkyl aromatic compounds, and the catalyst contains at least 2 parts by weight HF per part of BF3.

5. The process of claim 4 wherein the amount of HF-BF catalyst is from about 40 to about 60 weight percent and the catalyst contains at least about 10 parts by weight HF per part of BF 6. The process of claim 5 wherein the temperature is from about 15 C. to about 35 C. and the reaction time is from about 1 to about 2.5 hours.

7. The process of claim 6 wherein the aromatic moiety is phenyl and the alkyl group contains from about 10 to about 15 carbon atoms.

8. A process for disproportionating monoalkylben zones to dialkylbenzenes, said monoalkylbenzenes being in a mixture containing monoalkylbenzenes and tetrahydronaphthalenes, without concurrently producing a significant increase in the amount of tetrahydronaphthalenes in the reaction product, the alkyl group of said monoalkylbenzenes and each of the alkyl groups of said dialkylbenzenes containing at least 8 carbon atoms, said process consisting essentially of:

(a) contacting a mixture of monoalkylbenzenes and tetrahydronaphthalenes with HF-BF catalyst for from about 0.5 to about 6 hours at a temperature of from about 0 to about C.,

(b) recovering said dialkylbenzenes from the reaction product of step (a).

9. The process of claim 8 wherein the alkyl group of said monoalkylbenzenes and each of the alkyl groups of said dialkylbenzenes contains from 8 to 18 carbon atoms and is linear.

10. The process of claim 9 wherein the amount of HF- BF catalyst is from about 20 to about weight percent, based on said mixture of monoalkylbenzenes and tetrahydronaphthalenes, and the catalyst contains at least 2 parts by weight HF per part of B1 11. The process of claim 10 wherein the amount of HF-BF catalyst is from about 40 to about 60 weight percent and the catalyst contains at least about 10 parts by weight HF per part of BF 12. The process of claim 11 wherein the temperature is from about 15 C. to about 35 C. and the reaction time is from about 1 to 2.5 hours.

13. The process of claim 12 wherein the alkyl group contains from about 10 to about 15 carbon atoms.

14. The process of claim 13 wherein the temperature is about 25 C. and the reaction time is about 1.5 hours.

References Cited UNITED STATES PATENTS 2,688,643 9/1954 Dean et al 260671 2,753,384 7/1956 Lien et a1. 260668 3,173,965 3/1965 Pappas et a1 260667 3,288,716 11/1966 Becraft et al 252-59 3,316,294 4/1967 Feighner et a1. 260505 3,391,210 7/1968 Feighner et a1 260671 3,392,206 7/1968 Hurley et al 260671 3,352,933 11/1967 Sorgenti 260668 3,355,508 11/1967 Moulden 2 260-671 DELBERT E. GANTZ, Primary Examiner G. E. SCHMITKONS, Assistant Examiner US. Cl. X.R. 252-59; 260671 

